[pulseaudio-discuss] PulseAudio, Ubuntu 9.10 Karmic, SigmaTel STAC9200

Lennart Poettering lennart at poettering.net
Mon Oct 5 15:01:14 PDT 2009

On Tue, 29.09.09 19:49, Kyle Mallory (kyle.mallory at utah.edu) wrote:

> I'm experiencing an odd problem with PulseAudio on Ubuntu Karmic
> 9.10-a6.  I wasn't quite sure what was happening, but I made a video
> that hopefully better illustrates the problem.  I'm hopeful that
> someone can point me to a simple solution, or recommend a bug-fix.
> There isn't any audio, which is fine, but in particular take note of
> what PulseAudio is doing to the ALSA mixer.
> http://www.vimeo.com/6825531
> This is the problem I'm having on my laptop, with Karmic and
> PulseAudio on a SigmaTel STAC9200 audio chipset (Dell Precision
> M90).
> When using the volume keys on the front of the laptop, the volume
> levels on the ALSA mixer adjust the Master first, and then after
> muting Master, subsequently adjust the PCM and LFE levels.

Yes, PA controls the entire pipeline from the PCM stream to your
hw. We start with the 'outermost' mixer element, and set it to the dB
value that is nearest but larger than the volume we want to configure
the hw to. Then we go on to the next mixer element and set try to
configure the remaining volume value, all the way to the last
element. Normally that means that "Master" does the biggest volume
adjustment, while "PCM" is set to some value next to 0dB. This should
be ideal to get the best range and granularity of software control
from the hw.

> On my laptop, this results in very little volume control, and an
> overly bassy response as the LFE is maintained at full volume, while
> the master levels are dropped. Near the bottom of the volume range
> on the Notify window, the master volume is muted. Eventually the PCM
> and LFE levels are lowered through the last few 'presses' of the
> volume keys, and finally muted.
> Any help, suggestions, or ideas would be appreciated.  I use my
> laptop for video editing, and a fubared audio mixer is really a
> deal-breaker.

IIUTC then you have one of those laptops which are equipped with an
extra LFE speaker which signal is synthesized in hw from the stereo
signal we output? We don't fully cover that special hw right now,
sorry. And I am till now sure how we could ever cover that proplery.

There have been requests in the past that the LFE should always be
kept in sync with our volume. Which is what we do right
now. Previously we were always setting it to -inf dB. 


Lennart Poettering                        Red Hat, Inc.
lennart [at] poettering [dot] net
http://0pointer.net/lennart/           GnuPG 0x1A015CC4

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